Distribution of low-density lipoprotein-bound low-molecular-weight thiols: A new analytical approach

Human serum albumin Cys34 oxidative modifications following infiltration in the carotid atherosclerotic plaque

Objectives. To evaluate if the prooxidant environment present in atherosclerotic plaque may oxidatively modify filtered albumin. Methods. Fluorescein-5-maleimide labelled plasma samples and plaque extracts from 27 patients who had undergone carotid endarterectomy were analysed through nonreducing SDS-PAGE for albumin-Cys³⁴ oxidation. Furthermore, degree and pattern of S-thiolation in both circulating and plaque-filtered albumin were assayed. Results. Albumin filtered in the atherosclerotic plaque showed higher levels of Cys³⁴ oxidative modifications than the corresponding circulating form as well as different patterns of S-thiolation. Conclusions. Data indicate that the circulating albumin, once filtered in plaque, undergoes Cys³⁴ oxidative modifications and demonstrate for the first time that albumin is a homocysteine and cysteinylglycine vehicle inside the plaque environment.

Capillary electrophoresis with laser-induced fluorescence detection for ATP quantification in spermatozoa and oocytes

We describe a new capillary electrophoresis laser-induced fluorescence (CE-LIF) method for the quantification of adenosine 5'-triphosphate (ATP) in spermatozoa and oocytes. The optimization of the precapillary derivatization reaction between ATP and 4,4-difluoro-5,7-dimethyl-4-bora-3a,4adiaza-s-indacene-3-propionyl ethylene diamine hydrochloride (BODIPY FL EDA) has been described. BODIPY-ATP conjugate was analysed in an uncoated fused silica capillary of 75 μm ID and 50 cm effective length using a 10 mmol/L tribasic sodium phosphate buffer, pH 11.5, at 22 kV in <5 min. A good reproducibility of intra- and inter-assay tests was obtained (CV = 4.55% and 7.14%, respectively). With respect to our previous CE-UV assay, the new method showed an improvement in sensitivity that was about 120-fold (limit of quantification, 0.15 vs 18 μmol/L). Method applicability was proven on the reproductive cells of several animal species (roosters, horses, sheep and goats). Due to the elevated sensitivity, the new assay allows the measurement of adenosine 5'-triphosphate levels from just 20 oocytes. Considering that ATP concentration in reproductive cells is related to the mitochondrial integrity after cryopreservation, the proposed method could be a useful tool in assisted reproductive technologies.

Albumin-bound low molecular weight thiols analysis in plasma and carotid plaques by CE

We describe a new method for the quantification of low molecular weight thiols, as homocysteine, cysteine, cysteinylglycine, glutamylcysteine and glutathione bound to human plasma albumin. After albumin isolation and purification by SDS-PAGE, thiols were freed from protein with tri-n-butylphosphine and successively derivatized with 5-iodoacetamidofluorescein. Samples were then injected and quantified in about 18 min by CE with laser induced fluorescence detection. Precision tests indicate a good repeatability of the method both for migration times (RSD<0.63%) and areas (RSD<2.98%). The method allows to measure all five low molecular weight thiols released from just 3 microg of albumin thus improving the other described methods in which only three or four thiols were detected. Due to the elevated sensitivity (LOD of 0.3 pM for all thiols), also low molecular weight thiols bound to albumin filtered in tissues could be quantified.

Evaluation of low molecular mass thiols content in carotid atherosclerotic plaques

OBJECTIVES

Despite the evidence that both homocysteine and cysteine are important risk factors for vascular disease and atherosclerosis no information are reported about their effective amount in plaque and on the relationship with the other low molecular weight thiols.

DESIGN AND METHODS

We used capillary electrophoresis to measure thiols in both carotid plaque specimens and plasma samples from 37 patients undergoing carotid endarterectomy.

RESULTS

Pearson's correlation shows that intraplaque homocysteine, cysteine and cysteinylglycine levels are related to their plasma concentrations. The distribution of intraplaque GSH and Glu-Cys was higher than that of the same thiols in plasma, whereas the other thiols were significantly less prevalent in plaque than in plasma. Intraplaque haemoglobin and GSH levels were correlated, thus suggesting their common origin from erythrocytes lysis.

CONCLUSION

Data suggest that increased levels of intraplaque glutathione may induce important effects on plaque fate by perturbing the normal LMW thiol redox state.

Factors Affecting S-Homocysteinylation of LDL Apoprotein B

Background: Hyperhomocysteinemia is an important risk factor for vascular disease and atherosclerosis, but the mechanisms by which homocysteine exerts its deleterious effects are not known. Because oxidation and/or homocysteinylation may increase atherogenicity of LDL, we investigated S-homocysteinylation of LDL as a possible contributor to atherosclerosis pathogenesis.

Methods: We used capillary electrophoresis to measure LDL-bound thiols [homocysteine, cysteine (Cys), cysteinylglycine, glutathione, and glutamylcysteine] in 104 healthy study participants We also assessed total plasma thiol concentrations and lipid profiles.

Results: Our data suggest that apoprotein B (apoB)-cysteinylglycine (CysGly), apoB-Hcy, and apoB-Cys concentrations are markedly higher in men than in women. The percentage of CysGly and glutathione on apoB was higher than that of the same thiols in plasma, whereas the other thiols were markedly less prevalent in lipoprotein than in plasma. Pearson correlation showed that among all thiols, only total plasma Hcy is related to apoB-Hcy concentrations. Multiple correlation analysis confirmed that total Hcy was the most important determinant of apoB-Hcy. Age and LDL cholesterol also showed positive associations, but Cys and, mainly, CysGly were negatively associated with apoB-Hcy concentrations.

Conclusions: apoB-Hcy derivative formation is mainly dependent on total homocysteine concentration. Increased cholesterol concentrations are related to increased apoB-Hcy. CysGly seems to compete with Hcy for binding to LDL apoprotein, suggesting that CysGly may protect against atherosclerosis by decreasing the concentrations of Hcy transferred by LDL from plasma to endothelial and subendothelial spaces.